Is sending Line 23 WS switching signal disc dependent?

I've just got a Sony DAV-S880, which is SCARTless. Having lived in a pin 8 switching wonderland where everything worked fine, re: WS switching, I now find that some disks (eg Fellowship of the Ring) autoswitch to 16:9 fine while others (eg Ice Age) don't. TV signals from my TiVo swich fine.

This surprised me, as I presumed that the Line 23 signal (which is what I presume is switching Ring) is added by the player not embedded in the disk.

Can anyone enlighten me?

[LV426]

Is it possible that those that don't work are NTSC whereas those that do are PAL? If yes, then it's because line 23 is the PAL standard for the switching trigger; for NTSC it is another line (21?) and is is likely that the TV is only ever looking in one place (23) for the trigger.

All region 2 PAL....